An important property of a vehicle of this kind is its ability to travel over rough ground. The obstacles to be surmounted in this case can be of highly diverse forms, for example a staircase designed for humans which the vehicle must travel up or down, or a pipe fallen onto a floor. There are two main aspects to the security of such vehicles when surmounting such obstacles. One is stability, i.e., the ability of the vehicle not to topple over due to its own weight and that of its payload. The other is grip and relates to each of the propulsion units of the vehicle, i.e., the members which rest on the ground to support and displace or immobilize the vehicle. The "grip" of a propulsion unit is its ability not to slip excessively in contact with the ground, even if the surface state of the ground is locally unfavorable.
Another important property of a vehicle of this kind is its compactness: its overall dimensions, especially in the transverse and longitudinal directions, must preferably be sufficiently small for the vehicle to travel through narrow passages or corridors in a building designed only to admit a human operator
Another important property is that the vehicle should be as light as possible
Various vehicles have been designed to have a good ability to surmount obstacles safely.
A known vehicle has four tracked propulsion units which can tilt relative to the vehicle body. The track on each propulsion unit is guided by a number of guide members, including two sprocket wheels one of which is a drive sprocket wheel for driving the track. These units are carried by a propulsion unit body which is assembled to the vehicle body in such a way as to enable the propulsion unit to tilt about a transverse axis. The vehicle body carries drive and tilt motors for rotating the drive sprocket wheels through mechanical transmission systems and for driving the tilting movements of the propulsion units, respectively. These motors are provided with brakes for controlling these movements. The vehicle body further carries batteries for supplying electrical power and motor control means.
This known vehicle was designed by the Japanese company Mitsubishi and is known as the MRV (Multifunctional Robot Vehicle). It is described on pages 425 and 426 of the report on the "85 ICAR International Conference on Advanced Robotics, Sep. 9-10, 1985, Tokyo, Japan, organized by: Robotics Society of Japan, The Society of Biomechanisms, Japan Industrial Robot Association".
This prior art vehicle appears to be able to surmount obstacles of known shape. However, to enable it to do so, it must be controlled by a human operator who can see the obstacle, even if from a distance. Also, it would not seem to offer other above-mentioned important properties to a sufficient degree.